Method and apparatus for combined finger management and finger lock for a multipath signals in a wireless communication system

ABSTRACT

A method of managing fingers for multipath signals in a wireless communication device. In one embodiment, the present invention recites receiving multipath signals at a wireless communication device. The present embodiment then acquires one of the multipath signals in a searcher portion of the wireless communication device and determines a signal-to-noise ratio (SNR) level of the one multipath signal. Next, the present embodiment evaluates the multipath signal for categorization into one of a plurality of states and then generates a finger assignment by selectively providing the multipath signal for a demodulation operation based upon its state. The present embodiment then receives the finger assignment from the searcher portion of the communication device and determines a signal-strength for the finger assignment. The present embodiment then enables the finger assignment for a combine operation if the signal-strength for the finger assignment satiates a first signal-strength threshold. The present embodiment also prevents the finger assignment from being deassigned if the signal-strength of the finger assignment satiates a second threshold, wherein the second signal-strength threshold is less than the first signal-strength threshold.

TECHNICAL FIELD

The present claimed invention relates to the field of digitalcommunication. Specifically, the present claimed invention relates to anapparatus and a method for managing and locking fingers used to receivemultipath signals.

BACKGROUND ART

Wireless telephony, e.g. mobile phone use, is a widely-used mode ofcommunication today. Variable rate communication systems, such as CodeDivision Multiple Access (CDMA) spread spectrum systems, are among themost commonly deployed wireless technologies. Because of increasingdemand and limited resources, a need arises to improve their capacity,fidelity, and performance.

Referring to prior art FIG. 1A, an illustration of multipath signalpropagation between a conventional base station and a mobile phone isshown. A conventional base station 104 transmits a signal to a mobilestation, e.g., phone, 102. Typically, the signal contains pilotinformation, that identifies the base station, and data information,such as voice content. A signal that can be transmitted directly tomobile phone 102 without interference, such as first signal 106 a,provides the strongest signal. However, given the power limitations atwhich base station 104 can transmit the signal, and given the noise asignal may pick up, a need arises to improve the power and the SNR ofthe signal received at mobile phone.

Conventional methods will combine the portions of the transmitted signalthat travel different paths to mobile unit 102. The multiple paths arisebecause of natural and man-made obstructions, such as building 108, hill110, and surface 112, that deflect the original signal. Because of thepaths over which these other signals travel, a time delay andperformance deterioration intrinsically arises in thesynchronization-sensitive and noise-sensitive data transmitted from basestation 104 to mobile phone 102. However, to provide the strongestpossible signal to a mobile phone, two or more of the signals from thesemultiple paths, e.g. path 106 a-106 d, may be combined. However, toefficiently combine and demodulate multipath signals, a need arises fora method to select the most worthwhile candidates from all the differentmultipaths received in mobile phone.

Corruption of a transmitted signal falls into two general categories:slowly-varying channel impairment and fast fading variation.Slowly-varying channel impairment arises from factors such as log-normalfading, or shadowing caused by movement or blocking as exemplified inprior art FIG. 1A, or slow fading. Slower variations, e.g., sub Hz,determine in effect, the “availability” of the channel. In contrast,only the fast fading variation affects the details of the receivedwaveform structure and the interrelationships of errors within amessage. Hence, a need arises for a method that effectively choose theproperties of the signal that influence its condition for demodulation.

Referring now to prior art FIG. 1B, a graph of two conventionalmultipath signal strengths over time is shown. Graph 100 b has anabscissa 122 of time and an ordinate of signal-to-noise ratio (SNR) 120,e.g. pilot EC/Io ratio. Third multipath signal 106 c and fourthmultipath signal 106 d are shown as exemplary multipath signals receivedat mobile phone 102. Conventional methods typically select forcombining, the multipath signals with the highest SNR. Thus, at timespan A 124 a, the dark line representing fourth multipath signal 106 dhas a higher SNR level than third multipath signal 106 c, assuming bothsignals have the same noise level. However, at time span B 124 b, thedashed line representing third multipath signal 106 c has a higher SNRlevel. Given the closeness of the SNR, or of the signal to noise ratio,of these two multipath signals, the choice as to which signal will bechosen for the demodulator can oscillate back and forth.

This oscillation is a condition known as “thrashing.” The drawback withthrashing is that it consumes a significant amount of system resources,such as processor operations. During thrashing, the processor can beoverloaded with operations that constantly assign and deassign themultiple demodulators to different multipath signals. Furthermore,thrashing may degrade the quality of the mobile phone 102 output signal,as the switching may cause a loss of data or an audible interference orit may introduce latency effects. Consequently, a need arises for amethod to select the best multipath signal for combining while avoidingthe effect of thrashing.

Furthermore, referring again to prior art FIG. 1A, conventional methodscombine transmitted signals that travel different paths to mobile unit102. The multiple paths arise because of natural and man-madeobstructions, such as building 108, hill 110, and surface 112, thatdeflect the original signal. Because of the paths over which these othersignals travel, a time delay and performance deterioration intrinsicallyarises in the synchronization-sensitive and noise-sensitive data that istransmitted from base station 104 to mobile unit 102. To provide thestrongest possible signal to a mobile unit, two or more of the signalsfrom these multiple paths, e.g. path 106 a-106 d, may be combined.

Corruption of a transmitted signal falls into two general categories:slowly-varying channel impairment and fast fading variation.Slowly-varying channel impairment arises from factors such as log-normalfading, or shadowing caused by movement or blocking from objects, asshown in prior art FIG. 1A, or from slow fading. Slower variations,e.g., sub Hz, determine in effect, the “availability” of the channel. Incontrast, only the fast fading variation affects the details of thereceived waveform structure and the interrelationships of errors withina message. Interference on a signal can be caused by moving objects thattemporarily block the signal, such as moving object 113 that interfereswith signal 106 b of prior art FIG. 1A. Based upon the characteristicdifferences of these signals, a need arises for a method of capturing asignal while avoiding the detrimental characteristics of fast fading orshort fading variation encountered at the receiving unit.

Referring now to FIG. 1C, a flowchart of a conventional process used forimplementing fingers in a communication device is shown. Flowchart 100 cbegins with step 1002. In step 1002, an inquiry determines whether anassigned signal fails to meet a threshold for combining. If an assignedsignal does fail to the single threshold, then flowchart 100 c ends. Ifthe assigned signal satisfies the threshold, then flowchart 100 c ends.In step 1004, the finger assignment is immediately deassigned, e.g.because it failed to meet the threshold. Following step 1004, flowchartproceeds to step 1006. In step 1006, the communication device waits forthe searcher to assign a new finger.

Prior art FIG. 1C presents several problems associated with theconventional management of assigned fingers. The first problem dealswith thrashing. The second problem deals with unnecessary latency. Instep 1002, the only criteria by which fingers are deassigned is a singlethreshold for combining the signal. By using only a single threshold,third multipath signal 106 c is immediately deassigned, per step 1004,as soon as it fails the threshold. Because of this limitation, one ofthe demodulating fingers must now wait for the searcher to identify anew multipath signal to be assigned, e.g., per step 1006. This latencyoccurs where third pilot 106 c is deassigned and second multipath signal106 b is assigned.

In a different scenario, if no other multipath signals are available fordemodulation, and a demodulating finger is available, then secondmultipath signal 106 b may be constantly assigned and deassigned fromthe given demodulating finger based on its performance. That is, secondmultipath signal 106 b frequently crosses the threshold value, therebycausing the communication device to frequently assign, deassign, andreassign a multipath signal to a demodulating finger that has no otherworthy candidate multipath signals. This phenomenon of frequentassigning and deassigning is referred to as “thrashing.” Unfortunately,thrashing consumes a significant amount of system resources, such as CPUoperations, by constantly performing tasks such as assigning anddeassigning. Furthermore, thrashing may downgrade the quality of theoutput signal from the mobile unit 102. This is because the frequentchanges in finger assignment, and its associated latency effects, maycause an perceptible degradation in the composite signal provided by thecommunication device to a user. Consequently, a need arises for a methodof managing assigned fingers that avoids the problem of thrashing, andits associated side-effects.

Thus, an apparatus and a method are needed to improve the capacity,fidelity, and performance of digital communication. More specifically, aneed arises for a method to improve the power and the SNR of the signalreceived at mobile phone. In particular, a need arises for a method toselect the most worthwhile candidates from all the different multipathsreceived in mobile phone for a subsequent demodulation and combiningoperation. Additionally, a need arises for a method which meets theabove needs and which selects the best multipath signal for combiningwhile avoiding the effect of thrashing. A further need exists for amethod which meets the above needs and which captures a signal whileavoiding the detrimental characteristics of fast fading variationencountered at the receiving unit. Specifically, a need exists toprevent the problem of latency caused by frequent or unnecessary changesin finger assignment.

DISCLOSURE OF THE INVENTION

The present invention provides an apparatus and a method which improvethe capacity, fidelity, and performance of digital communication. Morespecifically, the present invention provides a method to improve thepower and the SNR of the signal received at mobile phone. The presentinvention further provides a method to select the most worthwhilecandidates from all the different multipaths received in mobile phonefor a subsequent demodulation and combining operation. The presentinvention further provides a method which achieves the aboveaccomplishments and which selects the best multipath signal forcombining while avoiding the effect of thrashing. The present inventionfurther provides a method which achieves the above accomplishments andwhich captures a signal while avoiding the detrimental characteristicsof fast fading variation encountered at the receiving unit.Specifically, the present invention prevents the problem of latencycaused by frequent or unnecessary changes in finger assignment.

Specifically, in one embodiment, the present invention recites receivingmultipath signals at a wireless communication device. The presentembodiment then acquires one of the multipath signals in a searcherportion of the wireless communication device and determines asignal-to-noise ratio (SNR) level of the one multipath signal. Next, thepresent embodiment evaluates the multipath signal for categorizationinto one of a plurality of states and then generates a finger assignmentby selectively providing the multipath signal for a demodulationoperation based upon its state. The present embodiment then receives thefinger assignment from the searcher portion of the communication deviceand determines a signal-strength for the finger assignment. The presentembodiment then enables the finger assignment for a combine operation ifthe signal-strength for the finger assignment satiates a firstsignal-strength threshold. The present embodiment also prevents thefinger assignment from being deassigned if the signal-strength of thefinger assignment satiates a second threshold, wherein the secondsignal-strength threshold is less than the first signal-strengththreshold.

These and other objects and advantages of the present invention willbecome obvious to those of ordinary skill in the art after having readthe following detailed description of the preferred embodiments whichare illustrated in the various drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form part ofthis specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention. The drawings referred to in this description should beunderstood as not being drawn to scale except as specifically noted.

PRIOR ART FIG. 1A is an illustration of multipath signal propagationbetween a conventional base station and a cell phone.

PRIOR ART FIG. 1B is graph of two conventional multipath signalstrengths over time.

PRIOR ART FIG. 1C is a flowchart of a conventional process used forimplementing fingers in a communication device.

FIG. 2 is a block diagram of a communication device used to managesmultipath signals, in accordance with one embodiment of the presentinvention.

FIG. 3 is a graph of an exemplary multipath signal, to which a timethreshold and a SNR threshold is applied, in accordance with oneembodiment of the present invention.

FIG. 4 is a state diagram in which multipath signals may be categorized,in accordance with one embodiment of the present invention.

FIG. 5 is a flowchart of a process used to manage multipath signals in acommunication device, in accordance with one embodiment of the presentinvention.

FIG. 6 is a block diagram of the management functions performed on afinger assignment in a communication device, in accordance with oneembodiment of the present invention.

FIG. 7 is a block diagram of a communication device used for finger lockmanagement of assigned fingers, in accordance with one embodiment of thepresent invention.

FIG. 8 is a graph of the performance of one assigned finger over time ascompared with multiple performance thresholds, in accordance with oneembodiment of the present invention.

FIG. 9A is a state diagram of finger locking states into which a fingerassignment can be categorized, in accordance with one embodiment of thepresent invention.

FIG. 9B is a state diagram of timing states into which a fingerassignment can be categorized, in accordance with one embodiment of thepresent invention.

FIG. 9C is a flowchart of a process for implementing the state diagramsfor finger locking states and for timing states in a communicationdevice, in accordance with one embodiment of the present invention

FIG. 10 is a flowchart of a process used for finger lock management ofassigned fingers in a communication device, in accordance with oneembodiment of the present invention.

The drawings referred to in this description should be understood as notbeing drawn to scale except if specifically noted.

BEST MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to the preferred embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. While the invention will be described in conjunction with thepreferred embodiments, it will be understood that they are not intendedto limit the invention to these embodiments. On the contrary, theinvention is intended to cover alternatives, modifications andequivalents, which may be included within the spirit and scope of theinvention as defined by the appended claims. Furthermore, in thefollowing detailed description of the present invention, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. However, it will be obvious toone of ordinary skill in the art that the present invention may bepracticed without these specific details. In other instances, well-knownmethods, procedures, components, and circuits have not been described indetail as not to unnecessarily obscure aspects of the present invention.

Some portions of the detailed descriptions which follow, e.g., theprocesses, are presented in terms of procedures, logic blocks,processing, and other symbolic representations of operations on databits within a computer or digital system memory or on signals within acommunication device. These descriptions and representations are themeans used by those skilled in the digital communication arts to mosteffectively convey the substance of their work to others skilled in theart. A procedure, logic block, process, etc., is herein, and generally,conceived to be a self-consistent sequence of steps or instructionsleading to a desired result. The steps are those requiring physicalmanipulations of physical quantities. Usually, though not necessarily,these physical manipulations take the form of electrical or magneticsignals capable of being stored, transferred, combined, compared, andotherwise manipulated in a communication device or a processor. Forreasons of convenience, and with reference to common usage, thesesignals are referred to as bits, values, elements, symbols, characters,terms, numbers, or the like with reference to the present invention.

It should be borne in mind, however, that all of these terms are to beinterpreted as referencing physical manipulations and quantities and aremerely convenient labels to be interpreted further in view of termscommonly used in the art. Unless specifically stated otherwise asapparent from the following discussions, it is understood thatthroughout discussions of the present invention, terms such as“receiving,” “acquiring,” “determining,” “categorizing,” “evaluating,”“providing,” “enabling,” or the like, refer to the action and processesof a communication device or a similar electronic computing device, thatmanipulates and transforms data. The data is represented as physical(electronic) quantities within the communication devices components, orthe computer system's registers and memories, and is transformed intoother data similarly represented as physical quantities within thecommunication device components, or computer system memories orregisters, or other such information storage, transmission or displaydevices.

Referring now to FIG. 2, a block diagram of a communication device usedto manages multipath signals is shown, in accordance with one embodimentof the present invention. Communication device 200, e.g., a mobilestation or phone, includes two general sections of firmware 210 andhardware 220. Firmware section 210 includes processor 214 and memory216, coupled to each other via bus 202.

Hardware section 220 of FIG. 2 includes an antennae 202, a transceiver204, a searcher 224, and a rake receiver 226. The antennae 202 iscoupled to the transceiver 204 which in turn is coupled to rake receiver226 and searcher 224. Searcher 224 and rake receiver 226 are bothcoupled to processor 214 and memory 216. Rake receiver 226 includesmultiple demodulation paths, also known as demodulating fingers ordemodulators, 221-223. Each finger 221-223 is coupled to transceiver 204so that it may independently identify and demodulate its respectivemultipath signal based upon its time of arrival. Rake receiver iscoupled to subsequent hardware, not shown in FIG. 2, that is well knownin the art for further processing of the signals. The output ofdemodulating fingers are coherently combined by a diversity combiner 225to produce maximum SNR. By using a combination of hardware 220 andfirmware 210, the present invention provides efficient and flexiblemanagement of multipath signals for efficient use of demodulators, asdescribed more fully hereinafter.

Referring now to FIG. 3, a graph of an exemplary multipath signal, towhich a time threshold and a SNR threshold is applied is shown, inaccordance with one embodiment of the present invention. Graph 300 hasan abscissa of time 322 and an ordinate of SNR 320, which can also beillustrative of signal power, assuming a constant noise level. Fourthmultipath signal 106 d is shown as an exemplary signal charted over aperiod of time. A first SNR threshold, multipath acceptance threshold(T_ACCEPT) 326, represents the threshold for which the multipathmanagement will consider a multipath ACCEPT operation for the multipathsignal in question. In conjunction with the T_ACCEPT 326 threshold, thepresent embodiment also shows the number threshold of measurement foracceptance (N_ACCEPT) 322 that represents a time threshold over whichthe signal-to-noise ratio of the signal must be maintained aboveT_ACCEPT wherein the signal strength of the multipath signal is aboveT_ACCEPT for N_ACCEPT consecutive times of searcher measurements. Asshown in FIG. 3, fourth multipath signal 106 d fails to satiate boththese thresholds in time span 3 343. However, fourth multipath signal106 d does satiate both of these thresholds as shown in time span 1 341.While the present embodiment utilizes both a SNR threshold and a timethreshold to consider a multipath ACCEPT operation for the multipathsignal, the present invention is well-suited to using only a SNRthreshold.

FIG. 3 also shows a second SNR threshold, multipath rejection threshold(T_REJECT) 328, which represents the threshold for which the multipathmanagement will consider a REJECT operation for the multipath signal inquestion. In conjunction with the T_REJECT 328 threshold, the presentembodiment also shows the number threshold of measurement for rejection(N_REJECT) threshold 324 that represents a time threshold over which thestrength of the signal must be below T_REJECT for the multipath REJECToperation to proceed. As shown in FIG. 3, fourth multipath signal 106 ddoes not satiate both these thresholds as shown by time span 2 342. Byusing a time threshold for accepting and/or rejecting a multipath signalwith respect to the demodulation and combining operations, the presentinvention essentially provides a low pass filtering for the signalevaluation. By doing so, the present invention limits the rate ofunnecessary assignment to noise signal and unnecessary deassignment ofdemodulating fingers from a perturbating but otherwise strong multipathsignal without causing thrashing. While the present embodiment utilizesboth a SNR threshold and a time threshold to consider a multipath ACCEPToperation for the multipath signal, the present invention is well-suitedto using only a SNR threshold.

FIG. 4 is a state diagram in which multipath signals may be categorized,in accordance with one embodiment of the present invention. Statediagram 400 shows three states: a temporary state 402, a potential state404, and an assigned state 406. These states are arranged in a hierarchywhere temporary state 402 is the lowest state, potential state 404 isthe next higher state, and assigned state 406 is the highest state.While the present embodiment shows three states, the present inventionis well suited to using any number of states in any kind of hierarchyarrangement. In the present embodiment, a demodulating finger isassigned to each multipath signals categorized in assigned state and themultipath signal is enabled for demodulation. In contrast, the multipathsignals categorized in any state other than assigned state are notenabled for demodulation, but can be maintained to evaluate performanceover time, and thus provide future candidates for demodulation.

By having more multipath signals associated with the temporary orpotential state, the present invention provides a ready supply ofgood-quality signals available for demodulation. This avoids some of thescheduling problems of finding a signal for an available demodulatingfinger, encountered in the prior art. Overall, the number of signalsassociated with all of the multiple states can greatly exceed the numberof available demodulating fingers in a rake receiver. In this manner,the present invention provides a sequence of queues of availablemultipath signals that will compensate for a wide variety of signalproblems.

FIG. 4 also shows how multipath signals are categorized, e.g. promotedand demoted, to and from specific states. The column labeled promotion410 provides a process whereby a multipath signal may be promoted to, orcategorized as, a certain state. Conversely, a column labeled demotion440 provides a process whereby a multipath signal may be demoted from acertain state. While the present embodiment provides a specific processfor categorizing a signal with a state, the present invention is wellsuited to using a wide variety of processes and methods adaptable tospecific applications.

The process of assigning a state for the present embodiment, shown inpromotion column 410, starts with a searcher signal input 420 from ahardware portion 462 of a communication device. FIG. 2 provides oneembodiment of hardware that implements input 420, where antennae 202 andtransceiver 204 and searcher combine to provide a multipath signal(signal).

Step 422 of the present embodiment inquires whether the signal has a SNRthat is greater than a predetermined threshold T_USE established by thesearcher. The threshold T_USE guarantees sufficient signal strength fordemodulation. If the signal does have a SNR that is greater thanthreshold T_USE, then the process proceeds to step 426. Alternatively,if the signal does not have a SNR that is greater than threshold T_USE,then the signal is rejected per step 450. The searcher measures anarrival time of the multipath signal with signal strength above T_USE.If the arrival time of the multipath signal does not match that of anyof the multipath signals existing in the multipath list, the multipathsignal is considered to be a new multipath signal.

Step 424 of the present embodiment inquires whether the new multipathsignal has a SNR that is greater than a threshold T_ACCEPT. If the newmultipath signal does have a SNR that is greater than thresholdT_ACCEPT, then the process proceeds to step 426. Alternatively, if thenew multipath signal does not have a SNR that is greater than thresholdT_ACCEPT, then the new multipath signal is rejected per step 450.

Step 426 of the present embodiment inquires whether the new multipathsignal is indeed a new pilot, e.g. a signal from a new base stationhaving a new pilot identification. If the new multipath signal is a newpilot, then the process categorizes the new multipath signal topotential state 404. This special treatment for a new base stationproduces better cell diversity gain. Alternatively, if the new multipathsignal is not a new pilot, then the process categorizes the newmultipath signal to temporary state 402.

If the arrival time of the multipath signal in the search result matchesthat of one of the multipath signals existing in the multipath list, thearrival time and the signal-to-noise ratio of the multipath list isupdated. This update process continues until arrival time and SNR of allthe multipath signals from the same base station are updated. Once thisupdate process finished, the rest of the steps in categorizationproceeds as follows.

In step 428 of the present embodiment, signals that are categorized intemporary state 402 are checked in subsequent searcher operations todetermine whether the signal maintains the SNR above T_ACCEPT, whichitself satisfies the SNR threshold, over a time threshold, e.g. overN_ACCEPT consecutive SNR measurements. If the signal satiates theN_ACCEPT threshold per step 428, then the signal is categorized inpotential state 404. Alternatively, if the signal does not satiate theN_ACCEPT threshold, then it remains categorized in temporary state 402.Step 428 is illustrated, in one embodiment, by the signal performance inFIG. 3. Both span 3 343 of signal 106 d span 1 341 satiate the T_ACCEPT326 threshold, but only span 1 342 satiates the N_ACCEPT 322 threshold.Consequently, at a time corresponding to span 3 343, signal 106 d wouldbe categorized in temporary state 402, while at time corresponding tospan 1 341, signal 106 d would be categorized in potential state 404.

In step 430 of the present embodiment, an inquiry determines whether ademodulating finger is not enabled and is available for demodulation.Step 430 is implemented in one embodiment by having one of demodulatingfingers in rake receiver 226 of FIG. 2 available for demodulating amultipath signal. If a demodulating finger is available, then the signalinitially categorized in potential state 404 is now categorized inassigned state 406 and thus the multipath signal is used fordemodulation or a demodulating finger is assigned to the multipathsignal. However, if a demodulating finger is not available, then theprocess proceeds to step 432.

In step 432 of the present embodiment, an inquiry determines whether thesignal satiates both T_COMP and N_COMP thresholds. The T_COMP thresholdrepresents a “comparison” margin threshold by which one signalcategorized in a potential state 404 has to exceed the SNR of anothersignal in assigned state 406 in order to be promoted to assigned state.The comparison margin threshold also includes a time threshold, N_COMPconsecutive SNR measurements, over which the T_COMP threshold issatiated. If a signal categorized in a potential state 404 has ongoingSNR performance that is greater than the SNR of one particular multipathin an assigned state 406 by more than T_COMP over N_COMP consecutivemeasurements, then the signal categorized in a potential state 404 ispromoted to an assigned state 406, and the signal categorized in anassigned state 406 is demoted to a potential state. If the two signalsswitch between assigned and potential states, then a demodulating fingeris reassigned from one multipath signal to another. Alternatively, if asignal SNR difference does not satiate T_COMP and N_COMP requirement,then the two signals remain categorized in original states. The purposeof these two thresholds is to only allow a signal categorized in anassigned state 406 to be replaced by a signal with substantially betterperformance in a consistent manner over time. This process avoidsconstant switching of states, e.g. thrashing, for signals when theirperformances are very close to each other. The present invention iswell-suited to using a wide range of values for T_COMP and N_COMP, asappropriate for a given application. For example, T_COMP and N_COMP canbe statically based upon T_ACCEPT and T_ACCEPT, or they can bedynamically based on actual values of SNR for signals categorized inassigned state 406.

The process of demoting from a state for the present embodiment, shownin demotion column 440, starts with a evaluating a performance of asignal that has been categorized in states 402-406. Step 442 inquireswhether the signal has a SNR that is less than T_REJECT, e.g. multipathREJECT thresholds that are shown in FIG. 2, over a time threshold, e.g.over N_REJECT consecutive SNR measurements. If a signal categorized inassigned state 406 has ongoing SNR performance that is less thanT_REJECT satiating the N_ACCEPT threshold, then the signal is demotedfrom assigned state 406, and rejected in step 450. Alternatively, if asignal categorized in assigned state 402 has ongoing SNR performancethat is not less than T_REJECT over N_REJECT consecutive measurements,then the signal remains categorized in assigned state 406. If a signalis demoted from assigned state 406, then a demodulating finger may openup or be deassigned, allowing step 430 to determine whether a signalcategorized in potential state 404 can be categorized in the higherassigned state 406.

Step 444 provides a process similar to that of step 442. In step 444, aninquiry determines whether the signal has a SNR that is less thanT_REJECT, e.g. multipath REJECT thresholds over N_REJECT consecutive SNRmeasurements. If a signal categorized in potential state 404 has ongoingSNR performance that is less than T_REJECT thresholds over N_REJECTconsecutive SNR measurements, then the signal is demoted from thepotential state 404, and rejected in step 450. Alternatively, if asignal categorized in potential state 404 has ongoing SNR performancethat is not less than T_REJECT over N_REJECT consecutive measurements,then the signal remains categorized in potential state 404.

Step 446 provides a process similar to that of step 442 but without timethreshold criterion. In step 446, an inquiry determines whether thesignal has a SNR that is less than T_ACCEPT. If a signal categorized intemporary state 402 has ongoing SNR performance that is less than T_thenthe signal is demoted from the temporary state 402, and rejected in step450. Alternatively, if a signal categorized in temporary state 402 hasongoing SNR performance that is not less than T_ACCEPT, then the signalremains categorized in temporary state 402.

The time thresholds utilized in process 400 can be implemented, in oneembodiment, by using various timers or counters that are activated atthe point during which an appropriate threshold is satisfied. Thepresent embodiment maintains a separate timer for each multipath signalassociated with potential state and assigned state, as required by step442 and 444. Thus, for example, a multipath REJECT timer implemented inhardware portion 220 of communication device 200, can be used toestimate the fading duration of the long-term fading channel. The timeris initiated when a multipath reject threshold value is satisfied, e.g.when a multipath signal's performance drops below a threshold T_REJECT,and is reset and disabled if the multipath signal exceeds the thresholdT_REJECT. Various defaults and expiration values can be established forthe times to accommodate zero threshold settings.

The process of categorizing signals into states, e.g. promoting them anddemoting them, per FIG. 4 is performed by the present embodiment byfirmware 210, such as that shown in FIG. 2. That is, states can berecorded in RAM portion 218 a of memory 216 of communication device 200.By using firmware, the present invention of managing demodulatingfingers can be quickly and easily modified to suit a particularapplication, such as continuing development discoveries. Thecategorizing of signals into states can be accomplished by a widevariety of methods, such as using flags, or allocating memory registersto states, etc.

Referring now to FIG. 5, a flowchart of the process used to managemultipath signals in a communication device is shown, in accordance withone embodiment of the present invention. By using process 5000embodiment, the present invention provides a method selects the mostworthwhile candidates from all the different multipaths received inmobile phone for a subsequent demodulation and combining operation,without the detrimental effects of thrashing. While the presentembodiment applies process 5000 to a CDMA digital communication system,the present invention can be applied to any communication system needingtime tracking. Also, the present invention is applicable to both mobileunits and base stations used for telecommunications operations.

Process 5000 begins with step 5002. In step 5002 of the presentembodiment, multipath signals are received at a communication device.Step 5002 is implemented, in one embodiment, by the hardware 220 shownin FIG. 2. In one embodiment, multipath signals, such as those shown inprior art FIG. 1A, are received by antennae 202 and transceiver 204 ofFIG. 2. Following step 5002, process 5000 proceeds to step 5004.

In step 5004 of the present embodiment, one of the multipath signals isacquired in terms of arrival time and signal strength. This isaccomplished, in one embodiment, by a searcher portion 224 ofcommunication device 200 of FIG. 2, as is well-known in the art.Following step 5004, process 5000 proceeds to step 5006.

In step 5006 of the present embodiment, a SNR ratio is determined forthe multipath signal acquired. Step 5006 is implemented, in oneembodiment, by a searcher portion 224 in conjunction with a firmwareportion 210 of communication device 200 of FIG. 2, as is well-known inthe art. While the present embodiment utilizes SNR to determine thequality of the acquired multipath signal, the present invention is wellsuited to alternative benchmarks. Following step 5006, process 5000proceeds to step 5008.

In step 5008 of the present embodiment, the multipath signal acquired isevaluated for categorization into one of a plurality of states. Step5006 is implemented, in one embodiment, by a firmware portion 210 ofcommunication device 200 of FIG. 2. In one embodiment, process 400 isused to evaluate the categorization of signals into one of a pluralityof states. However, the present invention is well-suited to using a widevariety of methods and criteria for evaluating a signal forcategorization into a state. Following step 5008, process 5000 proceedsto step 5010.

In step 5010 of the present embodiment, an inquiry determines whetherthe state of the signal is acceptable for demodulation. If the state ofthe acquired multipath signal is acceptable for demodulation, then theprocess 5000 proceeds to step 4012. Alternatively, if the state of theacquired multipath signal is not acceptable for demodulation, thenprocess 5000 proceeds to end.

In step 5012 of the present embodiment, the multipath signal is providedfor a demodulation operation. Step 5012 is implemented, in oneembodiment, by firmware 210 and hardware 220 portions of communicationdevice 200 of FIG. 2. Specifically, the timing requirements for theacquired multipath signal are provided from firmware 2120 to one of thedemodulating fingers, e.g. 221-223, in rake receiver 226 ofcommunication device 200 to enable demodulation of the given multipathsignal. Following step 5012, process 5000 proceeds to step 5014.

Process 5000 can be repeated to accommodate a number of significanttiming factors. In one embodiment, the pilots in the active set ofassigned-state and potential state signals available for demodulationcan be sampled in one visit. In another embodiment, they may be visitedseveral times in a search period, each time measuring all or some of thepilots in the active set. In order to guarantee a minimum search rate ofthe active set, the mobile station has a periodic search timer for theactive set such that the strength and pseudonoise (PN) phase of allpilots in the active set at least one per period.

Many of the instructions for steps and the data stored in memory 222 forprocess 300, are executed using processor 220. The memory storage forthe present embodiment can either be permanent, such as read only memory(ROM), or temporary memory such as random access memory (RAM). Memory216 can also be any other type of memory storage, capable of containingprogram instructions, such as a hard drive, a CD ROM, or flash memory.Furthermore, processor 214 can either be an existing system processor,or it can be a dedicated digital signal processing (DSP) processor.Alternatively, the instructions may be implemented using amicrocontroller or some other state machine.

Because the demodulating finger management process shown by process 5000uses data stored as software, the present invention provides dynamicmanagement. For example, thresholds used in process 5000 can be storedin memory. Thus, their values can be changed, in one embodiment.Threshold values can be programmed into ROM 218 b or RAM 218 a portionsof memory 216. Threshold values can be provided or changed viainstructions and data at the time the device is manufactured or it canbe communicated to the device while the device is in service with auser.

While process 5000 of the present embodiment shows a specific sequenceand quantity of steps, the present invention is suitable to alternativeembodiments. For example, not all the steps provided for process 5000are required for the present invention. And additional steps may beadded to those presented. Likewise, the sequence of the steps can bemodified depending upon the application. Furthermore, while process 5000is shown as a single serial process, it can also be implemented as acontinuous or parallel process. For example, instead of proceeding toend step, process 5000 could return to the start step for a secondmultipath signal after finishing step 4012 for a first multipath signal.

Many of the instructions for the steps, and the data input and outputfrom the steps of process 5000 is implemented utilizing memory 216 andutilizing processor 214, as shown in FIG. 2. Memory storage 216 of thepresent embodiment can either be permanent, such as read only memory(ROM) 218 b, or temporary memory such as random access memory (RAM) 218a. Memory 216 can also be any other type of memory storage, capable ofcontaining program instructions, such as a hard drive, a CD ROM, orflash memory. Furthermore, processor 214 can either be a dedicatedcontroller, an existing system processor, or it can be a dedicateddigital signal processing (DSP) processor. Alternatively, theinstructions can be implemented using some form of a state machine.

The present embodiment is comprised of two major parts. Specifically,the present embodiment first determines the most worthwhile candidatesfrom all the different multipaths (i.e. fingers) received in a searcherportion of a wireless communication system (in a manner as has beendescribed above in detail in conjunction with FIGS. 2-5). Second, (aswill be discussed below in detail in conjunction with FIGS. 6-10) thepresent embodiment then employs a novel method and apparatus to lock thepreviously finger and keep the finger appropriately assigned. In sodoing, the present embodiment both manages (i.e. selects the mostappropriate of available fingers) and locks (i.e. maintains thepreviously selected fingers in the most appropriate assigned state)fingers in a wireless communication system.

Referring now to FIG. 6, a block diagram of the management functionsperformed on a finger assignment in a communication device is shown, inaccordance with one embodiment of the present invention. Block diagram600 receives signal 640, transmitted from another device, e.g., basestation 104. SMC Block 642 (Set Maintenance Central processing unitsoftware) provides functions that such as channel estimation andsearcher functions to retrieve and assign multipath signals from the PNspace in the appropriate band for the communication device. SMC block642 functions are well-known in the art. In the present embodiment, SMCblock 642 functions according to the process described above in detailin, for example, process 5000 of FIG. 5.

Demodulating block 643 is coupled to SMC block 642. Demodulating block643 performs the function of demodulating multipath signals usingmultiple demodulating fingers. The quantity of fingers used can varywidely, with the specific quantity of fingers upon a specificapplication goal and its available resources.

Channel estimating (CHEST) block 644 is coupled to demodulating block643. CHEST block 644 provides a signal strength indication of a fingerassignment. In one embodiment, CHEST block 644 is a new function that isseparate from the channel estimator function performed by SMC block 642.In the present embodiment, CHEST block 644 performs dedicated channelestimation, and a more refined and accurate filtering operation, for agiven multipath signal of the assigned finger. CHEST block 644determines the E_(c)/I_(o) ratio (e.g. received pilot energy per chip,E_(c), divided by total received spectral density, I_(o)) and providesit, or a finger quality indicator (FQI), as output data 645 to the nextblock. In another embodiment, CHEST block 644 can use channel estimationdata that was performed in the SMC block 642, and simply perform anadditional filtering operation on that data. Channel estimators includefunctions that are well-known in the art for performing signal-strengthcalculations. For example, the CHEST block performs functions such asquadrature despreading, a sum and dump function, and an infinite impulseresponse (IIR) filter function. The IIR filter can have appropriatecoefficients, e.g., forgetting factors, specifically determined for aspecific application, given its performance goals and availableresources.

Finger lock block 646 is coupled to demodulating block 643, whichreceives the FQI data 645. Finger lock block 646 performs a logicfunction that interprets the E_(c)/I_(o) data 645 received from CHESTblock 644 and/or timer data 651 received from timer block 649. Fingerlock block evaluates signal strength data 645 and timer data 651 againstappropriate signal-strength thresholds and/or time thresholds to decidewhether the multipath signal should be deassigned, locked, orsubsequently combined. Details on the quantity, type, and values ofthresholds is described in more detail in subsequent figures. Fingerlock block 646 provides a finger combine indicator (FCI) output data 647to the next block to which it is coupled, e.g., the combiner block 648.

Combiner block 648 combines, if directed by the FCI data 647 from fingerlock block 646, multipath signals that were demodulated by the assignedfingers. If FCI data indicates that a multipath signal demodulated by afinger assignment should not be combined, then combiner block 648 doesnot combine it. Alternatively, if FCI data from finger lock block 646indicates that a multipath signal demodulated by a finger assignmentshould be combined, then combiner block 648 does combine it. Combinerblock 648 provides composite signal output 650 that is decoded bysubsequent function blocks that are not shown, but are well known in theart.

By using a CHEST block 644 to provide more accurate data on signalstrength, and by using logic and multiple thresholds implemented byfinger lock block 646 and timing block 649, the present inventionprovides an accurate and efficient buffer for holding assigned fingersduring short-term fading. In contrast, the prior art would drop fingerassignments during short term fading, and reassign them when theyrecovered, thus causing the undesirable effect of thrashing.

Referring now to FIG. 7, a block diagram of a communication device usedfor finger lock management of assigned fingers is shown, in accordancewith one embodiment of the present invention. Communication device 700,e.g., a mobile or base unit, includes two general sections:firmware/software 710 and dedicated hardware 720. Firmware/softwaresection 710 includes processor 714 and memory 716, coupled to each othervia bus 702. Firmware/software section 710 can be a general purposedevice, or a specialized digital signal processing (DSP) device.Alternatively, the functions performed by firmware/software section 710can be implemented using a specialized state machine.

Hardware section 720 of FIG. 7 includes an antennae 703, a transceiver704, and a rake receiver 726. Hardware section 720 is coupled tofirmware/software portion 710 of communication device 710 to provide theraw data with which the firmware/software section can digitally process.Antennae 703 is coupled to transceiver 704, which is in turn coupled torake receiver 726.

Bus 702 provides an exemplary coupling configuration of devices incommunication system 700. Bus 702 is shown as a single bus line forclarity. It is appreciated by those skilled in the art that bus 702 caninclude subcomponents of specific data lines and/or control lines forthe communication of commands and data between appropriate devices. Itis further appreciated by those skilled in the art that bus 702 caninclude numerous gateways, interconnects, and translators, asappropriate for a given application.

The present embodiment of FIG. 7 shows that rake receiver 726 includesthree fingers, e.g. finger 1 721, finger 2 722, and finger 3 723.However, the present invention is well-suited to using any quantity offingers in rake receiver 726. Each finger 721-723 is coupled totransceiver 704 so that it may independently identify and demodulate itsrespective multipath signal. By using a combination of hardware 720 andfirmware 710, the present invention provides efficient and flexiblemanagement of finger assignments for multipath signals, as describedmore fully hereinafter.

Transceiver 704, processor 714, and memory 716 of FIG. 7 performfunctions of SMC block 642 of FIG. 6, in one embodiment. Similarly,functions performed by demodulation block 643, channel estimator block644, finger lock block 646, timer block 649, and combiner block 648 ofFIG. 6 can be implemented by rake receiver 726, processor 714, and/ormemory 716 of FIG. 7, in one embodiment.

It is also appreciated that communication system 700 is exemplary onlyand that the present invention can operate within a number of differentcommunication systems. Furthermore, the present invention is well-suitedto using a host of intelligent devices that have similar components asexemplary communication system 700.

Referring now to FIG. 8, a graph of the performance of one assignedfinger over time as compared with multiple performance thresholds isshown, in accordance with one embodiment of the present invention.Subsequent figures will utilize this performance curve as an example toillustrate the functions and the present invention's processes, e.g.managing assigned fingers.

Graph 800 has an abscissa of time 822 and an ordinate of signal-strength820. Signal-strength can represent absolute signal power or some versionof signal to noise ratio (SNR) such as E_(o)/I_(c), describedhereinabove. Second multipath signal 106 b is shown as an exemplarysignal charted over a period of time. Graph 800 illustrates multiplethresholds used in the present invention. A first signal-strengththreshold, Threshold Combine (T_COMB) 826, represents the threshold bywhich the management process of the present invention approves a fingerassignment for a subsequent combine operation.

In conjunction with the T_COMB 826 threshold, the present embodimentalso includes a second signal-strength threshold of Threshold Lock(T_LOCK) 828. In the present embodiment, T_LOCK 828 has a lower valuethan T_COMB 826. T_LOCK threshold 828, represents the threshold by whichthe management process of the present invention decides whether to lockor deassign a finger assignment.

The third, and final, threshold is a time threshold, N_LOCK 824, whichrelates to the amount of time that a multipath signal exists between theT_COMB 826 and T_LOCK 828 thresholds. While the present embodimentprovides all three thresholds for evaluating the status of a multipathsignal of a finger assignment (e.g. for a subsequent combine or deassignoperation), the present invention is also suitable to using less thanall three thresholds. The specific values T_LOCK 828, T_COMB 826, N_LOCK824 can span a wide range of values, which are chosen depending uponrequirements and assumptions for the specific application, hardware,and/or protocol used for a communication system.

Still referring to FIG. 8, timespan 9 849, timespan 4 844, timespan 5845, and timespan 7 847, show performances of second multipath signal106 b that exceed T_COMB threshold 826. In contrast, timespan 6 846shows a performance of second multipath signal 106 b that fail tosatiate T_COMB threshold 828. Finally, timespan 1 841, and timespan 10850 show performances of second multipath signal 106 b that exceedT_COMB threshold 826. Multiple system cycles can occur over any of thetime spans listed in FIG. 8. Subsequent figures will refer to thesespecific timespan to illustrate the states and the processes of thepresent invention management of finger assignments.

Referring now to FIG. 9A, a state diagram of finger locking states intowhich a finger assignment can be categorized is shown, in accordancewith one embodiment of the present invention. State diagram 900 a showsthe virtual interaction between the states in which a finger assignmentmay be categorized and managed by the present invention. State diagram900 a will be used in subsequent figures to explain how the processesand equipment of the present invention effectively categorize andtransition multipath signal finger assignments in these states. Thethresholds referred to in FIG. 9A will be referenced to specifictimespans of exemplary signal in FIG. 8 so as to provide explicitexamples of state categorization and state transitions.

State diagram 900 a of FIG. 9A shows states available for a multipathsignal, as decided and provided by SMC (Set Maintenance Centralprocessing unit (CPU)) software, e.g. by SMC block 642 of FIG. 6described hereinabove. Multipath signals can have either of two statesprovided by SMC block 642 in FIG. 9A. The first state is an assignedstate 902, having a prerequisite condition that the pilot portion of themultipath signal have a signal-strength, e.g. E_(c)/I_(o), that isgreater than (>) the threshold for adding (T_ADD). The T_ADD thresholdused by a searcher is well-known in the art; its description is omittedherein for purposes of clarity. In the present embodiment, T_ADD has alower value than either T_LOCK or T_COMB.

The second state provided by the SMC block 642 of FIG. 9A is a deassignstate 904. One condition for maintaining a multipath signal, previouslycategorized in deassigned state 904, in the deassigned state 904, iswhen the pilot portion of the multipath signal has a signal-strength,e.g. E_(c)/I_(o), that is less than (<) the threshold for adding(T_ADD). Multipath signals categorized in locked state 906 or combinedstate 908 can be degraded into deassigned state 904, as describedhereinafter. These conditions will be described hereinafter.

Finger lock function block 646 also provides multiple states for amultipath signal as shown in state diagram 900 a. The present embodimentshows that two states exist in finger lock function block 646. The firststate is a combined state 908. One condition by which a multipath signalcan be categorized in combined state 908 is via an initial condition950. Initial condition 950 occurs when multipath signal is initiallyassigned, by SMC block 642, e.g. the multipath signal in question wasnot in a combined or locked state in the immediately preceding cycle ofthe management process. In the present embodiment, the FQI, e.g.E_(c)/I_(o), does not necessarily need to satisfy T_LOCK or T_COMBthresholds, though it likely will. The initial condition occurs thefirst time a multipath signal designation (viz. specific PN offset)enters the assigned state. Timespan 9 849 of FIG. 8 illustrates thisstate change scenario, where it is assumed that multipath signal 106 dhas just been acquired by searcher in timespan 9 849. Timespan 4 844 ofFIG. 8 also illustrates the state change scenario, where secondmultipath signal 106 b has been deassigned by SMC block 642 at timespan6 846, and thus appears as a new multipath signal assignment from SMCblock 642.

Another condition whereby a multipath signal is categorized in combinedstate 908 is via an upgrade condition 958. Specifically, upgradecondition 958 occurs when a multipath signal previously categorized inthe locked state 906 has a finger quality indicator (FQI) that exceeds(>) T_COMB threshold. Timespan 7 847 of FIG. 8 illustrates this statetransition scenario where multipath signal 106 b is in a locked statebecause its FQI>T_LOCK threshold, but its timespan at this FQI is lessthan the N_LOCK threshold. One condition that allows a multipath signalto remain categorized in combined state 908 is a maintain condition 952,whose criteria is that the FQI of the multipath signal is greater thanT_COMB threshold. Timespan 5 845 of FIG. 8 illustrates this statescenario. A multipath signal categorized in combine state 908 isprovided for a subsequent combine operation 956.

For a multipath signal categorized in combined state 908, the fingercombine indicator (FCI) is set to one (1) to represent a state that themultipath signal can be combined in a subsequent combine operation. TheFCI can represent an actual binary bit that can be a set or clear flagin a digital logic circuit or in software.

The second state in finger lock function 646 is a locked state 906. Onecondition by which a multipath signal may enter lock state 906 is todowngrade condition 962 previously described. A multipath signalpreviously categorized in combined state 908 can be downgraded to alocked state 906 by downgrade condition 962. Downgrade condition 962occurs if multipath signal has FQI that is less than T_COMB but greaterthan T_LOCK. Timespan 1 841 of FIG. 8 illustrates this state changescenario. Similarly, a multipath signal previously categorized incombined state 908 can be downgraded to the SMC function block 642,where it can be categorized in deassigned state 904 by downgradecondition 966. Downgrade condition 966 occurs if multipath signal hasFQI that is less than T_LOCK for any period of time. Timespan 6 846 ofFIG. 8 illustrates this state change scenario.

One condition in which a multipath signal presently categorized inlocked state 906 can remain in locked state 906 is a maintain condition960. Maintain condition 960 occurs for a multipath signal, previouslycategorized in locked state 906, whose FQI is less than T_COMB butgreater than T_LOCK threshold, and whose timer has not exceeded timethreshold, T_(L) (e.g., T_(L) is greater than zero for a countdown timerconfiguration). Timespan 10 850 of FIG. 8 illustrates this locked statescenario because its timespan is not greater than N_LOCK 824, by visualobservation. The recover y of signal 106 b from timespan 10 illustratesa short-fade condition that did not create thrashing in a communicationsystem because of the present invention's finger assignment managementsystem.

A multipath signal previously categorized in locked condition 906 isdowngraded from locked condition 906 if it fails to satiate conditionsfor the lock state 906. Specifically, first downgrade condition 964 aoccurs if multipath signal has a FQI that is less than T_COMB thresholdand greater than T_LOCK threshold, but whose timer has exceeded the timethreshold, T_(L) (e.g., timespan 2 842 of FIG. 8 illustrates this statechange scenario because its timespan exceeds N_LOCK 824 threshold byvisual observation). Second downgrade condition 964 b occurs ifmultipath signal has a FQI that is less than T_LOCK threshold. Timespan6 846 of FIG. 8 illustrates this state scenario, assuming it wascategorized in lock state 906 at least once between timespan 9 849 andtimespan 6 846. When multipath signals are downgraded from locked state406, control of the finger is passed to SMC function 642. SMC canperform any function or state categorizing of multipath signal, such ascategorizing it in deassigned state 904, where it will remain so long asthe pilot E_(c)/I_(o) is less than T_ADD.

Multipath signals categorized in locked state 906 are monitored by atimer, activated upon initial categorization into this state.Additionally, multipath signals categorized in locked state 906 have FCIset to zero (0) so that the multipath signal in question is notavailable for the subsequent combine operation. In one embodiment, eachmultipath signal finger assignment is independent of other multipathsignal finger assignments. As such, more than one multipath signal canoccupy any one of the states presented in FIG. 9A. While the presentembodiment of FIG. 9A provides specific requirements for categorizing amultipath signal into a state, and for a transition between states, thepresent invention is well-suited to using alternative thresholds orconditions.

Referring now to FIG. 9B, a state diagram of timing states into which afinger assignment can be categorized is shown, in accordance with oneembodiment of the present invention. State diagram 900 b of FIG. 9Bworks in coordination with state diagram 900 a of FIG. 9A, to providethe timer state portion of the conditions required for the statecategorization and to provide the combine state changes of a multipathsignal to satisfy the finger management process of the presentinvention, as described more fully in subsequent figures.

Timing diagram 900 b includes two states, a preload state 970 and acount-down state 972. The present embodiment utilizes a count-downtimer. However, the timer function can be accommodated by a count-uptimer that is compared against a threshold, with appropriate indicatinglogic. The timer function can be implemented by hardware, such as timerblock 728 of FIG. 7.

Preload state 970 sets the time threshold, T_(L), to N_LOCK 824, shownin FIG. 8. If the multipath signal does not enter a locked state, thenit remains unlocked, per maintain condition 973. However, if multipathsignal changes to a locked state, then the timer changes states percondition 974. The timer state can return from the countdown state 972to preload state 970 if multipath signal becomes unlocked, per condition978.

Countdown timer state 972 decrements the countdown timer for a givenmultipath signal. Multipath signal remains in countdown state if itssignal-strength causes it to remain in a locked state, shown ascondition 976. The decrement in countdown timer can be a samplingoccurrence where signal quality is determined, e.g. once per systemoperational cycle. This decrement can be correlated to a desiredspecific time value. For example, timer threshold can be set for 10cycles in a 5 MHz system, or 20 cycles in a 10 MHz system, to obtain thesame duration of short-fade. The timer states can also change if thetimer expires, shown as condition 980 in FIG. 9B. The timer expirationalso causes a change in the finger locking states of the multipathsignal, per FIG. 9A.

While state diagrams 900 a and 900 b of FIGS. 9A and 9B, in the presentembodiment, define thresholds in terms of inequalities, e.g. operandssuch as “>” or “<,” the present invention is also well-suited to usingother operands such as “≧” or “≦” to define the pass/fail criteria for athreshold.

Referring now to FIG. 9C, a flowchart of a process for implementing thestate diagrams for finger locking states and for timing states in acommunication device is shown, in accordance with one embodiment of thepresent invention. Flowchart 9000 c essentially provides one embodimentof the sequence of queries that can satisfy the state categorizationsand state transitions of FIGS. 9A and 9B. However, the present inventionis well-suited to using alternative sequences, queries, and processes toaccomplish the aforementioned state conditions. The steps of flowchart9000 c can be implemented by the various components of communicationdevice 700 of FIG. 7. In particular, the queries and the logic ofprocess 9000 c can be implemented using a state machine or by usingfirmware/software 710 in combination with the hardware 720 components ofcommunication device 700.

Process 9000 c begins with step 9002. In step 9002 of the presentembodiment, a finger assignment is received at communication device.Step 9002 is implemented, in one embodiment, by one of the fingers shownin rake receiver 726 shown in FIG. 7. The multipath signal has alreadybeen determined and assigned for a finger by SMC block 642, implementedin firmware/software 710 of communication device 700. Following step9002, process 9000 c proceeds to step 9003.

In step 9003 of the present embodiment, the multipath signal assigned isdemodulated by a finger. Step 9003 is accomplished, in one embodiment,by rake receiver portion 726 of communication device 700, shown in FIG.7. Specifically, one of the multiple fingers is assigned to a signalfinger, e.g. finger 1 721, in rake receiver 726. The demodulation stepis well-known by those skilled in the art. Following step 9003, process9000 c proceeds to step 9006.

In step 9004 of the present embodiment, the finger quality indicator(FQI) is determined. Step 9004 is accomplished, in one embodiment, bysoftware/firmware 710 portion of communication device 700. Step 9004provides continuous signal-strength indicators, e.g. E_(o)/I_(c)calculations, for a given multipath signal. Following step 9004, process9000 c proceeds to step 9006.

In step 9006 of the present embodiment, an inquiry determines whetherthe multipath signal is a newly assigned signal, e.g. the multipathsignal was previously unassigned by a searcher. If the multipath, signalis a newly assigned signal, then the process 9000 c proceeds to step9007. Alternatively, if the multipath signal is not a newly assignedsignal, then process 9000 c proceeds to step 9008. Step 9006 providesthe logic for demodulating a newly acquired signal immediately, and thusavoiding latency associated with subsequent steps in process 9000 c.Step 9006 is one implementation of the logic used to implement initialstate condition 950 of state diagram 900 a shown in FIG. 9A.

Step 9007 arises if the multipath signal is a newly assigned signal, perstep 9006. In step 9007 of the present embodiment, a finger combineindicator (FCI) is set to a value of one (1). By setting FCI=1, step9007 provides a bit flag that will enable, in the present embodiment,the assigned multipath signal to be combined in subsequent operation.The present invention is well-suited to using alternative logic andalternative devices to accomplish the step of enabling the multipathsignal to be combined when the required performance conditions aresatiated, e.g. per conditions of state diagrams in FIGS. 9A and 9B.Following step 9007, process 9000 c proceeds to step 9013.

In step 9013 of the present embodiment, a combine operation isperformed. Step 9013 is performed only on those signals with a FCI=1,which indicates that the signal is of sufficient quality to improve theoverall composite signal that results from the combine operation. Thealternative state of FCI=0 is discussed in a subsequent step. Step 9013implements the combine operation 956 of state diagram 900 a shown inFIG. 9A. Following step 9013, process 9000 c ends.

Step 9008 arises if the assigned multipath signal is not a newlyassigned signal, per step 9006. In step 9008 of the present embodiment,an inquiry determines whether the FQI is greater than the T_COMBthreshold. If the multipath signal has an FQI greater than the T_COMBthreshold, then the process 9000 c proceeds to step 9009. Alternatively,if the multipath signal has an FQI that is not greater than the T_COMBthreshold, then the process 9000 c proceeds to step 9010. Step 9008provides the logic for evaluating a first signal-strength threshold,T_COMB, shown in FIG. 8 as T_COMB threshold 826. Step 9008 is oneimplementation of the logic used to distinguish between combine state908 and locked state 906, per state change condition 958, state changecondition 962, and state maintain condition 960, of state diagram 900 ashown in FIG. 9A.

Step 9009 arises if the multipath signal has an FQI greater than theT_COMB threshold, per step 9008. In step 9009 of the present embodiment,the timer is cleared. This condition accounts for the scenario where themultipath signal has sufficient signal-strength, e.g. above T_COMBthreshold, such that the timer threshold is not of concern.Consequently, the timer is cleared to remove any residual values orstates that may have existed. This step can also be applicable for anewly assigned signal, per step 9006, though it is not part of thepresent embodiment. Following step 9009, process 9000 c proceeds to step9007, described hereinabove.

Step 9010 arises if the multipath signal has an FQI that is not greaterthan the T_COMB threshold, per step 9008. In step 9010 of the presentembodiment, an inquiry determines whether the FQI of the multipathsignal in question is less than the T_LOCK threshold. If the multipathsignal has an FQI less than the T_LOCK threshold, then the process 9000c proceeds to step 9011. This condition accounts for the scenario wherethe multipath signal does not have sufficient signal-strength, e.g.below T_LOCK threshold, to even remain a potential candidate forcombining. In particular, this scenario represents deep fading that issignificant enough to render assigned multipath signal unworthy of alocked state. Alternatively, if the multipath signal has an FQI that isnot less than the T_LOCK threshold, then the process 9000 c proceeds tostep 9012. This condition accounts for the scenario where the multipathsignal does have sufficient signal-strength, e.g. above T_LOCKthreshold, that it has a high probability of quickly returning to aneven higher signal-strength, e.g. T_COMB, which is suitable for thesubsequent combining operation.

Step 9010 provides the logic for evaluating a second signal-strengththreshold, T_LOCK, shown in FIG. 8 as T_LOCK threshold 828. Step 9010 isone implementation of the logic used to distinguish between combinestate 908 and locked state 906 and deassign state 904, per state changecondition 964 b and state maintain condition 960, of state diagram 900 ashown in FIG. 9A.

Step 9011 can arise under several conditions, in the present embodiment.First, step 9011 can arise if the multipath signal has an FQI less thanthe T_LOCK threshold, per step 9010. Second, step 9011 can arise if atimer for multipath signal exceeds N_LOCK threshold, per step 9014. Instep 9011, control of the finger assignment is yielded to the searcher,which will most likely deassign the multipath signal in question.However, the present invention is well-suited to alternativedispositions for multipath signal, other than the locked state. Becausethe multipath signal is removed from the locked state conditions, thetimer is cleared to remove any residual values or states that may haveexisted. This step can also be applicable for a newly assigned signal,per step 9006, though it is not part of the present embodiment.

Step 9012 arises if the multipath signal has an FQI that is less thanT_COMB threshold per step 9008 and an FQI that is greater than theT_LOCK threshold, per step 9010. In step 9012 of the present embodiment,the timer is stepped. This condition accounts for the scenario where themultipath signal has sufficient signal-strength, e.g. above T_LOCKthreshold, that it has a high probably of quickly returning to an evenhigher signal-strength, e.g. T_COMB, suitable for the subsequentcombining operation. However, to monitor the speed of the recovery ofthe signal-strength for the assigned multipath signal in question, thetimer is stepped, or incremented. The timer can either be a count-up ora count-down timer, as previously discussed for FIGS. 6 and 7. Step 9012can be implemented similarly to the implementation of step 9009.Following step 9012, process 9000 c proceeds to step 9014.

In step 9014 of the present embodiment, an inquiry determines whetherthe timer designated for the assigned multipath signal in question failsto satisfy the N_LOCK threshold. In the present embodiment, the N_LOCKthreshold 824 is shown in FIG. 8 as a given span of time. Thus, amultipath signal fails the threshold if the signal exceeds the amount oftime provided by the N_LOCK threshold. If the multipath signal doesexceed the N_LOCK threshold, then process 9000 c proceeds to step 9011.Alternatively, if the multipath signal does not exceed the N_LOCKthreshold, then process 9000 c proceeds to step 9016. Step 9014 providesthe logic for evaluating a time threshold for the signal-strengthperformance. That is, if the assigned multipath signal does not improveits signal-strength within the given period of time, e.g. N_LOCK, thenit has a low probability of recovering from its fade condition. Step9014 is one implementation of the logic used to distinguish betweenlocked state 906 and deassigned state 904, per state change condition964 a, state maintain condition 960, of state diagram 900 a shown inFIG. 9A. Step 9014 also provides one implementation of the logic used toaccommodate the timing state diagram 900 b of FIG. 9B.

Step 9015 arises if the multipath signal fails to satiate the timingthreshold, N_COMB, per step 9014. Step 9015, in the present embodiment,locks the finger assignment. This step is indirectly accomplished by notallowing the finger assignment to be combined per step 9013 and by notyielding control of the assigned finger to the searcher, where it wouldmost likely be deassigned. Thus, the present embodiment of a finger lockis temporarily implemented. Following step 9015, process 9000 c proceedsto step 9016.

In step 9016 of the present embodiment, the finger combine indicator(FCI) is set to a value of zero (0). Step 9016 is accomplished, in amanner similar to that described in step 9007, discussed hereinabove,albeit opposite polarity. By setting FCI=0, step 9016 provides a bitflag that will disable, in the present embodiment, the assignedmultipath signal from being combined in a subsequent operation.Following step 9016, process 9000 c returns to step 9002.

Many of the instructions for the steps, and the data input and outputfrom the steps of process 9000 c can be implemented utilizing memory 716and utilizing processor 714, as shown in FIG. 7. The memory storage forthe present embodiment can either be permanent, such as read only memory(ROM), or temporary memory such as random access memory (RAM). Memory716 can also be any other type of memory storage, capable of containingprogram instructions, such as a hard drive, a CD ROM, or flash memory.Furthermore, processor 714 can either be an existing system processor,or it can be a dedicated digital signal processing (DSP) processor.Alternatively, the instructions may be implemented using amicrocontroller or a state machine.

While process 9000 c of the present embodiment shows a specific sequenceand quantity of steps, the present invention is suitable to alternativeembodiments. For example, not all the steps provided for process 9000 care required for the present invention. And additional steps may beadded to those presented. Likewise, the sequence of the steps can bemodified depending upon the application. Furthermore, while process 9000c is shown as a single serial process, it can also be implemented as acontinuous or parallel process.

Referring now to FIG. 10, a flowchart of the process used for fingerlock management of assigned fingers in a communication device is shown,in accordance with one embodiment of the present invention. By usingprocess 1000 embodiment, the present invention provides a method ofimplementing multiple thresholds, including an optional time threshold,to manage an assigned multipath signal for a demodulating finger. Byadaptively managing the assigned multipath signal, the present inventionavoids latency and thrashing problems associated with conventionalcommunication systems. As a result of implementing the presentinvention, capacity, fidelity, and performance of a digitalcommunication system is enhanced. The process of the present inventionis applicable to any type of communication device, such as mobile units(e.g. cell phones) and base stations.

Process 1000 begins with step 1002. In step 1002 of the presentembodiment, a finger assignment, e.g., an active multipath signaldesignation, is received at a communication device. Step 1002 isimplemented, in one embodiment, using the function blocks described inFIG. 6, using the devices described in FIG. 7, and/or using the methoddescribed in FIG. 9C. Step 1002 is also well-suited to using thealternatives described for these function blocks, devices, and methodsof prior figures. Following step 1002, process 1000 proceeds to step1003.

In step 1003 of the present embodiment, the finger assignment isprovided to a demodulating finger where it is demodulated. Step 1003 isimplemented, in one embodiment, by step 9003 of FIG. 9C. Following step1003, process 1000 proceeds to step 1004.

In step 1004 of the present embodiment, a performance level of a fingerassignment is determined. Step 1002 is implemented, in one embodiment,by step 9004 of FIG. 9C. However, step 1004 is well-suited to thealternative methods for determining a performance level of a fingermentioned for step 9004. Outputs from step 1004 include signal-strength1004 a and time period 1004 b over which signal-strength 1004 a exists.Outputs 1004 a and 1004 b can be implemented using the embodiments andalternatives provided in FIGS. 6 through 9C. Output 1004 b of timeperiod provides a useful tool for evaluating the duration of fading onthe signal-strength of a finger assignment. This, in turn, allows thepresent invention to provide adaptive combining of the finger assignmentbased on the time and signal-strength thresholds. Following step 1004,process 1000 proceeds to step 1006.

In step 1006 of the present embodiment, the finger assignment iscategorized into a state for a subsequent combine operation. Step 1006includes, in one embodiment, inputs of signal-strength 1006 a and timeperiod 1006 b over which the signal-strength exists. In anotherembodiment, a finger assignment can be categorized into a statedepending only upon multiple signal-strength thresholds. In anotherembodiment, a finger can be categorized into a state depending upon anadditional threshold of time. Step 1006 is implemented, in oneembodiment, according to state diagrams 900 a and 900 b, shown in FIGS.9A and 9B. The state machines are effectively implemented by statemachines and/or software/firmware 710 portions of communication device700. However, the present invention is well-suited to using alternativestate diagrams, with a wide range of conditions used to determine astate change or a state maintenance for a given multipath signal. Step1006 provides outputs of a lock state 1006 c and a timer state 1006 d.These outputs are implemented, in one embodiment, utilizing the statediagrams of FIGS. 9A and 9B, and utilizing the hardware 720 andsoftware/firmware 710 portions of communication device 700 of FIG. 7.Following step 1006, process 1000 proceeds to step 1008.

In step 1008 of the present embodiment, the finger assignment isevaluated for a combination operation based upon its performance level.Step 1008 is implemented, in one embodiment, by evaluating the state inwhich the finger assignment has been categorized. The state isimplicitly implemented using the finger combine indicator (FCI) flags,as described in FIG. 9C. This embodiment is implemented using hardware720 and software/firmware portion 710 of communication device 700, asdescribed for FIG. 7. The use of flag bits allows convenient andstreamlined implementation of states for deciding on the combinationoperation for a given finger assignment. However, the present inventionis well-suited to using an alternative method for implementing thedecision to combine, lock, or deassign a finger assignment based on themultiple thresholds mentioned in the present embodiment. Following step1008, process 1000 proceeds to step 1010.

In step 1010 of the present embodiment the states of a finger assignmentare adaptively updated. Step 1010 is accomplished by the repeatedimplementation of process 9000 c of FIG. 9C in a parallel or serialmanner. The states can either be stored and updated in memory 716, orcan be implemented by hardware, of communication device 700 of FIG. 7.Following step 1010, process 1000 ends.

While process 1000 of the present embodiment shows a specific sequenceand quantity of steps, the present invention is suitable to alternativeembodiments. For example, not all the steps provided for process 1000are required for the present invention. And additional steps may beadded to those presented. Likewise, the sequence of the steps can bemodified depending upon the application. Furthermore, while process 1000is shown as a single serial process, it can also be implemented as acontinuous or parallel process.

Many of the instructions for the steps, and the data input and outputfrom the steps of process 1000 can be implemented utilizing memory 716and utilizing processor 714, as shown in FIG. 7. Memory storage 716 ofthe present embodiment can either be permanent, such as read only memory(ROM) 718 b, or temporary memory such as random access memory (RAM) 718a. Memory 716 can also be any other type of memory storage, capable ofcontaining program instructions, such as a hard drive, a CD ROM, orflash memory. Furthermore, processor 714 can either be a dedicatedcontroller, an existing system processor, or it can be a dedicateddigital signal processing (DSP) processor. Alternatively, theinstructions can be implemented using some form of a state machine.

Thus, the present invention provides an apparatus and a method whichimprove the capacity, fidelity, and performance of digitalcommunication. More specifically, the present invention provides amethod to improve the power and the SNR of the signal received at mobilephone. The present invention further provides a method to select themost worthwhile candidates from all the different multipaths received inmobile phone for a subsequent demodulation and combining operation. Thepresent invention further provides a method which achieves the aboveaccomplishments and which selects the best multipath signal forcombining while avoiding the effect of thrashing. The present inventionfurther provides a method which achieves the above accomplishments andwhich captures a signal while avoiding the detrimental characteristicsof fast fading variation encountered at the receiving unit.Specifically, the present invention prevents the problem of latencycaused by frequent or unnecessary changes in finger assignment.

The foregoing descriptions of specific embodiments of the presentinvention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The embodiments were chosen and described in order to bestexplain the principles of the invention and its practical application,to thereby enable others skilled in the art to best utilize theinvention and various embodiments with various modifications as aresuited to the particular use contemplated. It is intended that the scopeof the invention be defined by the Claims appended hereto and theirequivalents.

1. A method of managing fingers for multipath signals in a wireless communication device, said method comprising: receiving said multipath signals at said wireless communication device; acquiring one of said multipath signals in a searcher portion of said wireless communication device; determining a signal-to-noise ratio (SNR) level of said one of said multipath signals; evaluating said one of said multipath signals for categorization into one of a plurality of states using at least one SNR threshold; generating a finger assignment by selectively providing said one of said multipath signals for a demodulation operation based upon its state; receiving said finger assignment from said searcher portion of said communication device; determining a signal-strength for said finger assignment; enabling said finger assignment for a combine operation if said signal-strength for said finger assignment satiates a first signal-strength threshold; preventing said finger assignment from being deassigned if said signal-strength of said finger assignment satiates a second signal-strength threshold, said second signal-strength threshold being less than said first signal-strength threshold; and determining a time period over which said signal-strength of said finger assignment satiates said second signal-strength threshold but is below said first signal-strength threshold, wherein said finger assignment is allowed to be deassigned if said time period exceeds a time threshold.
 2. The method recited in claim 1 wherein said plurality of states includes three hierarchical states.
 3. The method recited in claim 1 wherein said plurality of states includes an assigned state, wherein signals associated with said assigned state are used for an active demodulation operation.
 4. The method recited in claim 1 wherein said plurality of states includes a potential state, wherein signals associated with said potential state are not actively used for an active demodulation operation, but which may be likely candidates for a future demodulation operation.
 5. The method recited in claim 1 wherein said plurality of states includes a temporary state, wherein signals associated with said temporary state are not actively used for an active demodulation operation, but which may be likely candidates for categorization in a potential state in a future evaluation.
 6. The method recited in claim 1 wherein said one of said multipath signals is categorized according to said SNR level of said one of said multipath signals.
 7. The method recited in claim 1 wherein said one of said multipath signals is categorized according to a time period over which said SNR level of said one of said multipath signals exists.
 8. The method recited in claim 3 further comprising: enabling said one of said multipath signals for said demodulation operation if it is categorized in said assigned state.
 9. The method recited in claim 1 wherein said receiving said multipath signals, acquiring, determining said SNR level, evaluating, and generating are repeated to provide a quantity of multipath signals at least equivalent to a number of fingers in a receiver portion of said wireless communication device.
 10. The method recited in claim 1 further comprising: preventing said finger assignment from being deassigned if said time period satiates said time threshold.
 11. The method recited in claim 1 further comprising: allowing said finger assignment to be deassigned if said finger assignment fails to satiate said second signal-strength threshold.
 12. The method recited in claim 1 further comprising: demodulating said finger assignment.
 13. The method recited in claim 1 further comprising: filtering said signal-strength of said finger assignment as determined in said signal-strength determining.
 14. The method of claim 1 further comprising: categorizing said finger assignment into one of a plurality of states based upon said signal-strength of said finger assignment.
 15. The method of claim 1 further comprising: categorizing said finger assignment into one of a plurality of states based upon said signal-strength of said finger assignment and based upon said time period over which said signal-strength exists.
 16. The method of claim 14 further comprising: evaluating said finger assignment for said combine operation or for deassignment based upon its state.
 17. A wireless communication device to manage multipath signals and to manage a finger assignment, said communication device comprising: a searcher adapted to scan for said multipath signals; a transceiver coupled to said searcher; a processor coupled to said searcher; and a computer readable memory unit coupled to said processor, said computer readable memory unit containing program instructions stored therein that execute, via said processor, and cause the processor to perform: receiving said multipath signals at said wireless communication device; acquiring one of said multipath signals in said searcher of said wireless communication device; determining a signal-to-noise ratio (SNR) level of said one of said multipath signals; evaluating said one of said multipath signals for categorization into one of a plurality of states using at least one SNR threshold; generating a finger assignment by selectively providing said one of said multipath signals for a demodulation operation based upon its state; receiving said finger assignment; determining a signal-strength for said finger assignment; enabling said finger assignment for a combine operation if said signal-strength for said finger assignment satiates a first signal-strength threshold; preventing said finger assignment from being deassigned if said signal-strength of said finger assignment satiates a second threshold, said second signal-strength threshold being less than said first signal-strength threshold; and determining a time period over which said signal-strength of said finger assignment satiates said second signal-strength threshold but is below said first signal-strength threshold, wherein said finger assignment is allowed to be deassigned if said time period exceeds a time threshold.
 18. The device recited in claim 17 wherein said plurality of states includes three hierarchical states.
 19. The device recited in claim 17 wherein said plurality of states includes an assigned state, wherein signals associated with said assigned state are used for an active demodulation operation.
 20. The device recited in claim 17 wherein said plurality of states includes a potential state, wherein signals associated with said potential state are not actively used for an active demodulation operation, but which may be likely candidates for a future demodulation operation.
 21. The device recited in claim 17 wherein said plurality of states includes a temporary state, wherein said temporary state is not actively used for an active demodulation operation, but which may be likely candidates for categorization in a potential state in a future evaluation.
 22. The device recited in claim 17 wherein said one of said multipath signals is categorized according to said SNR level of said one of said multipath signals.
 23. The device recited in claim 17 wherein said one of said multipath signals is categorized according to a time period over which said SNR level of said one of said multipath signals exists.
 24. The device recited in claim 19 wherein said stored program instructions further cause the processor to perform: enabling said one of said multipath signals for said demodulation operation if it is categorized in said assigned state.
 25. The device recited in claim 17 wherein said receiving said multipath signals, acquiring, determining said SNR level, evaluating, and generating are repeated to provide a quantity of multipath signals equivalent to, or greater than, a number of fingers in a receiver portion of said wireless communication device.
 26. The device recited in claim 17 wherein said stored program instructions further cause the processor to perform: preventing said finger assignment from being deassigned if said time period satiates said time threshold.
 27. The device recited in claim 17 wherein said stored program instructions further cause the processor to perform: allowing said finger assignment to be deassigned if said finger assignment fails to satiate said second signal-strength threshold.
 28. The device recited in claim 17 wherein said stored program instructions further cause the processor to perform: demodulating said finger assignment.
 29. The device recited in claim 17 wherein said stored program instructions further cause the processor to perform: filtering said signal-strength of said finger assignment as determined in said signal-strength determining.
 30. The device of claim 17 wherein said stored program instructions further cause the processor to perform: categorizing said finger assignment into one of a plurality of states based upon said signal-strength of said finger assignment.
 31. The device of claim 17 wherein said stored program instructions further cause the processor to perform: categorizing said finger assignment into one of a plurality of states based upon said signal-strength of said finger assignment and based upon said time period over which said signals strength exists.
 32. The method of claim 30 wherein said stored program instructions further cause the processor to perform: evaluating said finger assignment for said combine operation or for deassignment based upon its state.
 33. A computer readable medium containing computer readable codes stored therein that are executable by a processor to cause a wireless communication device to implement a method of managing multipath signals, by: receiving said multipath signals at said wireless communication device; acquiring one of said multipath signals in a searcher portion of said wireless communication device; determining a signal-to-noise ratio (SNR) level of said one of said multipath signals; evaluating said one of said multipath signals for categorization into one of a plurality of states using at least one SNR threshold; generating a finger assignment by selectively providing said one of said multipath signals for a demodulation operation based upon its state; receiving said finger assignment; determining a signal-strength for said finger assignment; enabling said finger assignment for a combine operation if said signal-strength for said finger assignment satiates a first signal-strength threshold; preventing said finger assignment from being deassigned if said signal-strength of said finger assignment satiates a second threshold, said second signal-strength threshold being less than said first signal-strength threshold; and determining a time period over which said signal-strength of said finger assignment satiates said second signal-strength threshold but is below said first signal-strength threshold, wherein said finger assignment is allowed to be deassigned if said time period exceeds a time threshold.
 34. The computer readable medium recited in claim 33 wherein said plurality of states includes three hierarchical states.
 35. The computer readable medium recited in claim 33 wherein said plurality of states includes an assigned state, wherein signals associated with said assigned state are used for an active demodulation operation.
 36. The computer readable medium recited in claim 33 wherein said plurality of states includes a potential state, wherein signals associated with said potential state are not actively used for an active demodulation operation, but which may be likely candidates for a future demodulation operation.
 37. The computer readable medium recited in claim 33 wherein said plurality of states includes a temporary state, wherein said temporary state is not actively used for an active demodulation operation, but which may be likely candidates for categorization in a potential state in a future evaluation.
 38. The computer readable medium recited in claim 33 wherein said one of said multipath signals is categorized according to said SNR level of said one of said multipath signals.
 39. The computer readable medium recited in claim 33 wherein said one of said multipath signals is categorized according to a time period over which said SNR level of said one of said multipath signals exists.
 40. The computer readable medium recited in claim 35 wherein said computer readable codes are further executable by said processor to implement the method of managing multipath signals, by: enabling said one of said multipath signals for said demodulation operation if it is categorized in said assigned state.
 41. The computer readable medium recited in claim 33 wherein said receiving said multipath signals, acquiring, determining said SNR level, evaluating, and generating are repeated to provide a quantity of multipath signals equivalent to, or greater than, a number of fingers in a receiver portion of said wireless communication device.
 42. The computer readable medium recited in claim 33 wherein said computer readable codes are further executable by said processor to implement the method of managing multipath signals, by: preventing said finger assignment from being deassigned if said time period satiates said time threshold.
 43. The computer readable medium recited in claim 33 wherein said computer readable codes are further executable by said processor to implement the method of managing multipath signals, by: allowing said finger assignment to be deassigned if said finger assignment fails to satiate said second signal-strength threshold.
 44. The computer readable medium recited in claim 33 wherein said computer readable codes are further executable by said processor to implement the method of managing multipath signals, by: demodulating said finger assignment.
 45. The computer readable medium recited in claim 33 wherein said computer readable codes are further executable by said processor to implement the method of managing multipath signals, by: filtering said signal-strength of said finger assignment as determined in said signal-strength determining.
 46. The computer readable medium recited in claim 33 wherein said computer readable codes are further executable by said processor to implement the method of managing multipath signals, by: categorizing said finger assignment into one of a plurality of states based upon said signal-strength of said finger assignment.
 47. The computer readable medium recited in claim 33 wherein said computer readable codes are further executable by said processor to implement the method of managing multipath signals, by: categorizing said finger assignment into one of a plurality of states based upon said signal-strength of said finger assignment and based upon said time period over which said signals strength exists.
 48. The computer readable medium recited in claim 46 wherein said computer readable codes are further executable by said processor to implement the method of managing multipath signals, by: evaluating said finger assignment for said combine operation or for deassignment based upon its state. 